Michigan Natural Features Inventory

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Plants and Animals

Sphaerium corneumEuropean pea clam

Key Characteristics

The European pea clam has a thin, oval-shaped, light brown to gray glossy shell of an average .3 inches in length. The shell is very inflated, being nearly as high as it is long, and finely striated dorsally, becoming ventrally more coarse. The beak is centrally located, low and broad.

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

As is common with freshwater mollusks in general, the European pea clam has shown high rates of absorption and bioaccumulation of chemical pollutants found in many herbicides and pesticides (Boryslawskyj et al. 1987, Heinonen et al. 1997). Heavy metals and increased sedimentation from agricultural/urban runoff also pose a threat, and maintainting high water quality should be a priority. Monitoring and mitigation for resident aquatic organisms should be put in place before major alterations to habitat such as river impoundment, dredging, or construction are undertaken. Invasions of zebra mussels, which outcompete pea clams for important food items, have been related to population declines in the Great Lakes region (Lozano et al. 2000, Nalepa et al. 1998). Preventing the spread of zebra mussels by cleaning boat hulls, trailers, and scuba/fishing gear before moving between waterbodies, will benefit this species.

Active Period

Survey Methods

Peaclams are best surveyed for by collecting with a grab sampler, such as an Ekman or Peterson grab, or dip net. Collected samples are washed through sieves with a fine mesh (.40 mm openings) in order to retain the smallest individuals. Light-duty forceps can be used to hand-pick peaclams from debris (Mackie 2007).

Mackie, G.L., D.S. White, and T.W. Zbeda. 1980. A Guide to Freshwater Mollusks of the Laurentian Great Lakes with Special Emphasis on the Genus Pisidium. EPA Report 600/3-80-068. Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Duluth. 144 pp.